Field of the Invention
The present invention relates to a substrate cleaning apparatus and a substrate cleaning method for use in a substrate processing apparatus, such as a plating apparatus for carrying out a sequence of plating steps on a surface of a substrate and drying the plated substrate, and more particularly to a substrate cleaning apparatus and a substrate cleaning method for cleaning a surface of a substrate held by a substrate holder with cleaning water, such as pure water, with a periphery of the substrate surface sealed by a sealing member after processing of the substrate, such as plating.
Description of the Related Art
The applicant has proposed a plating apparatus capable of successively forming bumps on a surface of a substrate, such as a semiconductor wafer. This plating apparatus includes a substrate holder for detachably holding the substrate by sandwiching it between a first holding member (base holding member) and a second holding member (movable holding member) while keeping a periphery of the substrate in pressure contact with an inner sealing member mounted to the second holding member and keeping the first holding member in pressure contact with an outer sealing member mounted to the second holding member so as to seal the contact portions. After plating of the surface of the substrate held by the substrate holder, the substrate surface is cleaned and dried while the substrate holder keeps holding the substrate (see Japanese Patent Laid-Open Publication No. 2003-247098).
This plating apparatus includes a water-cleaning bath (cleaning bath) as a substrate cleaning apparatus for cleaning the substrate after plating. The substrate held by the substrate holder is immersed in cleaning water, such as pure water, stored in the water-cleaning bath, so that the substrate and the substrate holder are cleaned simultaneously.
FIGS. 1A through 1E illustrate a sequence of cleaning processes according to a conventional typical substrate cleaning method for cleaning a substrate, such as a semiconductor wafer, together with the substrate holder by immersing the substrate held by the substrate holder in the cleaning water, such as pure water, in the cleaning bath.
First, as shown in FIG. 1A, a substrate holder 204 holding a substrate is lowered toward a cleaning bath 200 filled with cleaning water 202, such as pure water, and as shown in FIG. 1B the substrate held by the substrate holder 204 is immersed in the cleaning water 202 retained in the cleaning bath 200, so that the substrate and the substrate holder 204 in their entirety are cleaned with the cleaning water 202. This cleaning process is basically a process of removing a liquid chemical, adhering to the substrate and the substrate holder 204, by diffusion due to a difference in concentration of liquid.
Next, as shown in FIG. 1C, the cleaning water 202 into which the liquid chemical has been diffused through the cleaning process is discharged from the cleaning bath 200. Thereafter, as shown in FIG. 1D, fresh cleaning water 202 is supplied into the cleaning bath 200 to clean the substrate and the substrate holder 204 in their entirety. Such QDR (quick dump rinse) cleaning may be repeated multiple times, e.g., two or three times, as needed.
Next, as shown in FIG. 1E, the substrate holder 204 together with the substrate is pulled up from the cleaning water 202 to terminate the cleaning process. The lower a speed at which the substrate holder 204 is pulled up, the smaller is an amount of the cleaning water adhering to the substrate holder 204 and the substrate, leading to less contamination by e.g., a plating solution in the next process. The cleaning water 202 remaining in the cleaning bath 200 may be reused for cleaning the next substrate in order to reduce the amount of cleaning water (pure water) used.
There has been proposed a cleaning apparatus configured to clean a semiconductor wafer by supplying a jet of pure water to the semiconductor wafer through shower nozzles provided at a top portion and a side portion of a water-cleaning bath while discharging the supplied pure water from the water-cleaning bath, and subsequently supplying pure water into the water-cleaning bath to clean the semiconductor wafer (see Japanese Patent Laid-Open Publication No. S61-61425). There has also been proposed a cleaning apparatus configured to clean a semiconductor wafer by supplying a jet of pure water to the semiconductor wafer through shower nozzles provided at a top portion and a bottom portion of a water-cleaning bath while discharging the supplied pure water from the water-cleaning bath (see Japanese Patent Laid-Open Publication No. S62-160728).
In the conventional QDR method of cleaning the substrate surface with pure water immediately after plating, if the number of QDR cleaning operations is small, uneven drying (uneven oxidation) of the substrate surface can occur upon drying of the substrate. Such uneven drying of the substrate surface is caused by a high concentration of the plating solution contained in the cleaning water remaining on the substrate. Thus, if the concentration of the plating solution in the cleaning water is low, uneven drying of the substrate surface will not occur. The cleaning water remaining on the substrate is one that comes from the cleaning bath.
Therefore, in the conventional QDR cleaning method, it is necessary to lower the concentration of the plating solution in the cleaning water stored in the cleaning bath when cleaning the substrate with the cleaning water. As a result, the number of QDR cleaning operations is increased, resulting in an increased amount of cleaning water (pure water) used.
Furthermore, when the substrate is held by the substrate holder while sealing a periphery of the surface of the substrate with a sealing member, a continuous annular recess may be formed on a contact portion D1 (see FIG. 6) in the periphery of the substrate surface contacting the sealing member. In the conventional QDR cleaning method in which convection of the cleaning water in the cleaning bath is less likely to occur, the plating solution, adhering to the recess formed on the contact portion D1, is less diffused. As a result, it is difficult to remove the plating solution from the peripheral contact portion D1. In order to uniformly clean the entire surface, including the periphery, of the substrate, it is necessary to further increase the number of QDR cleaning operations.
The difficulty in cleaning the contact portion in the periphery of the substrate surface contacting the sealing member is also encountered when cleaning the substrate by supplying a jet of cleaning water from the cleaning nozzle (shower nozzle) to the substrate surface. In order to uniformly clean the entire surface including the periphery of the substrate without causing uneven drying, it is considered necessary to increase a flow rate of the jet of cleaning water.